Contact interlayer dielectric replacement with improved sac cap retention

ABSTRACT

Embodiments of the present invention are directed to reducing the effective capacitance between active devices at the contact level. In a non-limiting embodiment of the invention, an interlayer dielectric is replaced with a low-k material without damaging a self-aligned contact (SAC) cap. A gate can be formed over a channel region of a fin. The gate can include a gate spacer and a SAC cap. Source and drain regions can be formed adjacent to the channel region. A contact is formed on the SAC cap and on surfaces of the source and drain regions. A first dielectric layer can be recessed to expose a sidewall of the contact and a sidewall of the gate spacer. A second dielectric layer can be formed on the recessed surface of the first dielectric layer. The second dielectric layer can include a dielectric material having a dielectric constant less than the first dielectric layer.

BACKGROUND

The present invention generally relates to fabrication methods andresulting structures for semiconductor devices, and more specifically,to replacing a contact interlayer dielectric while improvingself-aligned contact (SAC) cap retention.

Traditional metal oxide semiconductor field effect transistor (MOSFET)fabrication techniques include process flows for constructing planarfield effect transistors (FETs). A planar FET includes a substrate (alsoreferred to as a silicon slab), a gate formed over the substrate, sourceand drain regions formed on opposite ends of the gate, and a channelregion near the surface of the substrate under the gate. The channelregion electrically connects the source region to the drain region whilethe gate controls the current in the channel. The gate voltage controlswhether the path from drain to source is an open circuit (“off”) or aresistive path (“on”).

In recent years, research has been devoted to the development ofnonplanar transistor architectures. For example, fin-type field effecttransistors (finFETs) employ non-planar body regions in which thechannel, source, and drain regions of the finFET are formed. A gate runsalong the sidewalls and a top surface of the channel portion of eachsemiconductor fin, enabling fuller depletion in the channel region, andreducing short-channel effects due to steeper subthreshold swing (SS)and smaller drain induced barrier lowering (DIBL).

SUMMARY

Embodiments of the invention are directed to a method for reducing theeffective capacitance between active devices at the contact level. Anon-limiting example of the method includes forming a gate over achannel region of a fin. The gate can include a gate spacer and a gatehard mask. Source and drain regions can be formed adjacent to thechannel region. A contact is formed on the gate hard mask and onsurfaces of the source and drain regions. A first dielectric layer canbe recessed to expose a sidewall of the contact and a sidewall of thegate spacer. A second dielectric layer can be formed on the recessedsurface of the first dielectric layer. The second dielectric layer caninclude a dielectric material having a dielectric constant less than thefirst dielectric layer. The contact prevents erosion of the gate hardmask when recessing the first dielectric layer.

Embodiments of the invention are directed to a method for reducing theeffective capacitance between active devices at the contact level. Anon-limiting example of the method includes forming a gate over achannel region of a fin. A SAC cap is formed over the gate and a contactis formed on the SAC cap. A first dielectric layer is formed on asidewall of the gate. The first dielectric layer can include a firstdielectric material having a first dielectric constant. The firstdielectric layer can be recessed to expose a sidewall of the contact anda second dielectric layer can be formed on a recessed surface of thefirst dielectric layer. The second dielectric layer can include a seconddielectric material having a second dielectric constant less than thefirst dielectric constant. The contact prevents erosion of the gate hardmask when recessing the first dielectric layer.

Embodiments of the invention are directed to a semiconductor structure.A non-limiting example of the semiconductor device includes a gate overa channel region of a fin. The gate includes a gate spacer and a gatehard mask. The semiconductor device can include a source adjacent to afirst end of the channel region and a drain adjacent to a second end ofthe channel region. The semiconductor device can include a first contacton a surface of the source and a second contact on a surface of thedrain. A first dielectric layer is formed on a sidewall of the firstcontact and on a sidewall of the second contact. The first dielectriclayer includes a first dielectric material having a first dielectricconstant. A second dielectric layer is formed on a surface of the firstdielectric layer. The second dielectric layer includes a seconddielectric material having a second dielectric constant less than thefirst dielectric constant. A first portion of the second dielectriclayer can be on a sidewall of the gate spacer and a second portion ofthe second dielectric layer can be on the sidewall of the first contactand on the sidewall of the second contact.

Additional technical features and benefits are realized through thetechniques of the present invention. Embodiments and aspects of theinvention are described in detail herein and are considered a part ofthe claimed subject matter. For a better understanding, refer to thedetailed description and to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The specifics of the exclusive rights described herein are particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features and advantages ofthe embodiments of the invention are apparent from the followingdetailed description taken in conjunction with the accompanying drawingsin which:

FIG. 1 depicts a top-down view of a semiconductor structure after aprocessing operation according to one or more embodiments of theinvention;

FIG. 2A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 2B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 2C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 3A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 3B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 3C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 4A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 4B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 4C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 5A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 5B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 5C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 6A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 6B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 6C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 7A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 7B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 7C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 8A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 8B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 8C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 9A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 9B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 9C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 10A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 10B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 10C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 11A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 11B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 11C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 12A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 12B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 12C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 13A depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X after a processing operation accordingto one or more embodiments of the invention;

FIG. 13B depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line X′ after a processing operation accordingto one or more embodiments of the invention;

FIG. 13C depicts a cross-sectional view of the semiconductor structureshown in FIG. 1 along the line Y after a processing operation accordingto one or more embodiments of the invention;

FIG. 14 depicts a flow diagram illustrating a method according to one ormore embodiments of the invention; and

FIG. 15 depicts a flow diagram illustrating a method according to one ormore embodiments of the invention.

The diagrams depicted herein are illustrative. There can be manyvariations to the diagram or the operations described therein withoutdeparting from the spirit of the invention. For instance, the actionscan be performed in a differing order or actions can be added, deletedor modified.

In the accompanying figures and following detailed description of thedescribed embodiments of the invention, the various elements illustratedin the figures are provided with two or three-digit reference numbers.With minor exceptions, the leftmost digit(s) of each reference numbercorrespond to the figure in which its element is first illustrated.

DETAILED DESCRIPTION

It is understood in advance that although example embodiments of theinvention are described in connection with a particular transistorarchitecture, embodiments of the invention are not limited to theparticular transistor architectures or materials described in thisspecification. Rather, embodiments of the present invention are capableof being implemented in conjunction with any other type of transistorarchitecture or materials now known or later developed.

For the sake of brevity, conventional techniques related tosemiconductor device and integrated circuit (IC) fabrication may or maynot be described in detail herein. Moreover, the various tasks andprocess steps described herein can be incorporated into a morecomprehensive procedure or process having additional steps orfunctionality not described in detail herein. In particular, varioussteps in the manufacture of semiconductor devices andsemiconductor-based ICs are well known and so, in the interest ofbrevity, many conventional steps will only be mentioned briefly hereinor will be omitted entirely without providing the well-known processdetails.

Turning now to an overview of technologies that are more specificallyrelevant to aspects of the present invention, recent contact resistivityimprovements has resulted in dramatic reductions in the “on-resistance”(RON) of finFET devices. As RON decreases, reductions in parasiticcapacitance become desirable. This is because parasitic capacitancecontributes to undesired device effects such as resistive-capacitive(RC) delay, power dissipation, and cross-talk. RC delay refers to thedelay in signal speed or propagation experienced in a circuit as afunction of the product of the resistance and capacitance of the circuitcomponents. In other words, reducing parasitic capacitance in low RONdevices is needed to optimize delay.

Various approaches to reduce parasitic capacitance in the conventionalfinFET process flow have been explored, to varying degrees of success.Conventional approaches (e.g., gate spacer air gaps), however, do notaddress the relatively large area between the active regions of thesubstrate. Addressing this area is difficult, as modifying the areabetween the active regions can result in inadvertently damaging thedevice, especially the self-aligned contact (SAC) cap used inconventional finFET process flows.

Turning now to an overview of aspects of the present invention, one ormore embodiments of the invention address the above-describedshortcomings of the prior art by providing a new semiconductor structureand method that reduces the effective capacitance between active devicesat the contact level by replacing the conventional interlayer dielectricoxide with an ultra low-k material (i.e., a material having a dielectricconstant less than about 3.0) using a scheme that retains a maximumamount of SAC cap. In some embodiments of the invention, a SAC cap isformed over a gate and a source/drain region is formed adjacent to thegate. A source/drain contact is formed on a surface of the source/drainregion. The source/drain contact is planarized to a surface of a hardmask formed over the SAC cap, ensuring that an overburden remains overthe SAC cap. This overburden protects the SAC from erosion duringsubsequent processing steps (e.g., the interlayer dielectric etch).After forming the overburden, a portion of the interlayer dielectric isremoved and replaced with an ultra low-k material.

In some embodiments of the invention, a selective cap material isdeposited over an exposed surface of the source/drain contact prior tothe interlayer dielectric etch back for additional protection. In someembodiments of the invention, a protective liner (e.g., a nitride liner)is deposited over the structure after the etch back, but prior todepositing the ultra low-k material. The protective liner provides abarrier between the source/drain contact metal and the ultra low-k (ULK)material, avoiding direct ULK deposition on the source/drain contactmetal. This protective liner can also strengthen a damaged SAC capand/or gate hard mask prior to downstream processes.

This new semiconductor structure and method results in a reduction inthe effective capacitance (and overall delay) of the active devices overcurrent integration schemes that utilize oxide between the activedevices, and does so without damaging the device. Advantageously,reducing the effective capacitance between active devices by replacing aconventional interlayer dielectric (e.g., an oxide having a dielectricconstant of about 4.5 when taking into account the presence of nitridespacers) with a lower dielectric constant material (e.g., a materialhaving a dielectric constant of less than or equal to about 3) canprovide up to a 4 percent improvement in delay.

Turning now to a more detailed description of aspects of the presentinvention, FIG. 1 depicts a top-down view of a semiconductor structure100 during an intermediate operation of a method of fabricating a finalsemiconductor device according to one or more embodiments of theinvention. In embodiments of the invention, the final semiconductordevice can be a variety of types of MOSFETs, including, for example,non-planar n-type field effect transistors (NFET) and p-type fieldeffect transistors (PFET). For example, the final semiconductor devicecan be an n-type finFET or a p-type finFET. In the embodiment shown inFIG. 1, the semiconductor structure 100 includes one or more gates 102formed over channel regions of one or more fins 104. The semiconductorstructure 100 can also include one or more trench silicide contacts 106.While described with respect to the finFET transistor architecture forease of illustration, it is understood that the method can be applied toother transistor architectures, such as, for example, nanosheet orgate-all-around transistor architectures.

As best shown in FIGS. 2A and 2C, the fins 104 are formed on a substrate202. The fins 104 can be formed on the substrate 202 using known FEOLfinFET fabrication techniques. The substrate 202 and the fins 104 can bemade of any suitable semiconductor material, such as, for example,monocrystalline Si, silicon germanium (SiGe), III-V compoundsemiconductor, II-VI compound semiconductor, orsemiconductor-on-insulator (SOI). Group III-V compound semiconductors,for example, include materials having at least one group III element andat least one group V element, such as one or more of aluminum galliumarsenide (AlGaAs), aluminum gallium nitride (AlGaN), aluminum arsenide(AlAs), aluminum indium arsenide (AlIAs), aluminum nitride (AlN),gallium antimonide (GaSb), gallium aluminum antimonide (GaAlSb), galliumarsenide (GaAs), gallium arsenide antimonide (GaAsSb), gallium nitride(GaN), indium antimonide (InSb), indium arsenide (InAs), indium galliumarsenide (InGaAs), indium gallium arsenide phosphide (InGaAsP), indiumgallium nitride (InGaN), indium nitride (InN), indium phosphide (InP)and alloy combinations including at least one of the foregoingmaterials. The alloy combinations can include binary (two elements,e.g., gallium (III) arsenide (GaAs)), ternary (three elements, e.g.,InGaAs) and quaternary (four elements, e.g., aluminum gallium indiumphosphide (AlInGaP)) alloys.

In some embodiments of the invention, the substrate 202 and the fins 104can be made of the same semiconductor material. In other embodiments ofthe invention, the substrate 202 can be made of a first semiconductormaterial, and the fins 104 can be made of a second semiconductormaterial. In some embodiments of the invention, the substrate 202 andthe fins 104 can be made of silicon or SiGe. In some embodiments of theinvention, the substrate 202 is silicon and the fins 104 are silicongermanium having a germanium concentration of about 10 to about 80percent. The fins 104 can each have a height ranging from 4 nm to 150nm. In some embodiments of the present invention, the fins 104 areformed to a height of about 60 nm, although other fin heights are withinthe contemplated scope of the invention.

In some embodiments of the invention, the substrate 202 can include aburied oxide layer (not depicted). The buried oxide layer can be made ofany suitable dielectric material, such as, for example, a silicon oxide.In some embodiments of the invention, the buried oxide layer is formedto a thickness of about 145 nm, although other thicknesses are withinthe contemplated scope of the invention. As best shown in FIG. 2A, insome embodiments of the invention, the semiconductor structure 100 canbe electrically isolated from other regions of the substrate 202 byshallow trench isolation (STI) regions 204.

As best shown in FIG. 2A, the one or more gates 102 can be high-k metalgates (HKMGs) formed over a channel region 216 of the fins 104 using,for example, known replacement metal gate (RMG) processes, or so-calledgate-first processes. The gates 102 can include a high-k dielectricmaterial(s) (not shown) and a work function metal stack (not shown). Insome embodiments, the gates 102 includes a main body formed from bulkconductive gate material(s).

In some embodiments of the invention, the gate dielectric is a high-kdielectric film formed on a surface (sidewall) of the fins 104. Thehigh-k dielectric film can be made of, for example, silicon oxide,silicon nitride, silicon oxynitride, boron nitride, high-k materials, orany combination of these materials. Examples of high-k materials includebut are not limited to metal oxides such as hafnium oxide, hafniumsilicon oxide, hafnium silicon oxynitride, lanthanum oxide, lanthanumaluminum oxide, zirconium oxide, zirconium silicon oxide, zirconiumsilicon oxynitride, tantalum oxide, titanium oxide, barium strontiumtitanium oxide, barium titanium oxide, strontium titanium oxide, yttriumoxide, aluminum oxide, lead scandium tantalum oxide, and lead zincniobate. The high-k materials can further include dopants such aslanthanum and aluminum. In some embodiments of the invention, the high-kdielectric film can have a thickness of about 0.5 nm to about 4 nm. Insome embodiments of the invention, the high-k dielectric film includeshafnium oxide and has a thickness of about 1 nm, although otherthicknesses are within the contemplated scope of the invention.

In some embodiments of the invention, the gates 102 include one or morework function layers (sometimes referred to as a work function metalstack) formed between the high-k dielectric film and a bulk gatematerial. In some embodiments of the invention, the gates 102 includeone or more work function layers, but do not include a bulk gatematerial.

If present, the work function layers can be made of, for example,aluminum, lanthanum oxide, magnesium oxide, strontium titanate,strontium oxide, titanium nitride, tantalum nitride, hafnium nitride,tungsten nitride, molybdenum nitride, niobium nitride, hafnium siliconnitride, titanium aluminum nitride, tantalum silicon nitride, titaniumaluminum carbide, tantalum carbide, and combinations thereof. The workfunction layer can serve to modify the work function of the gates 102and enables tuning of the device threshold voltage. The work functionlayers can be formed to a thickness of about 0.5 to 6 nm, although otherthicknesses are within the contemplated scope of the invention. In someembodiments of the invention, each of the work function layers can beformed to a different thickness. In some embodiments of the invention,the work function layers include a TiN/TiC/TiCAl stack.

In some embodiments, the gates 102 includes a main body formed from bulkconductive gate material(s) deposited over the work function layers. Thebulk gate material can include any suitable conducting material, suchas, for example, metal (e.g., tungsten, titanium, tantalum, ruthenium,zirconium, cobalt, copper, aluminum, lead, platinum, tin, silver, gold),conducting metallic compound material (e.g., tantalum nitride, titaniumnitride, tantalum carbide, titanium carbide, titanium aluminum carbide,tungsten silicide, tungsten nitride, ruthenium oxide, cobalt silicide,nickel silicide), conductive carbon, graphene, or any suitablecombination of these materials. The conductive gate material can furtherinclude dopants that are incorporated during or after deposition.

FIGS. 2A, 2B, and 2C depict cross-sectional views of the semiconductorstructure 100 taken along the lines X, X′, and Y of FIG. 1 after aprocessing operation according to one or more embodiments of theinvention. As illustrated in FIG. 2A, the fins 104 can be formed overthe substrate 202. As discussed previously, the STI region 204electrically isolates the fins 104 from other devices on the substrate202.

In some embodiments of the invention, spacers 208 (also known assidewall spacers or gate spacers) are formed on sidewalls of the gates102. In some embodiments of the invention, the spacers 208 are formed orpatterned prior to forming the source and drain regions 206. In someembodiments of the invention, the spacers 208 are formed on sidewalls ofa dummy gate that is replaced by the gates 102 during an RMG process. Insome embodiments of the invention, the spacers 208 are formed using achemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), ultrahighvacuum chemical vapor deposition (UHVCVD), rapid thermal chemical vapordeposition (RTCVD), metalorganic chemical vapor deposition (MOCVD),low-pressure chemical vapor deposition (LPCVD), limited reactionprocessing CVD (LRPCVD), atomic layer deposition (ALD), physical vapordeposition (PVD), chemical solution deposition, molecular beam epitaxy(MBE), or other like process in combination with a wet or dry etchprocess. For example, spacer material can be conformally deposited overthe semiconductor structure 100 and selectively removed using a RIE toform the spacers 208. The spacers 208 can be made of any suitablematerial, such as, for example, a low-k dielectric, a nitride, siliconnitride, silicon oxide, SiON, SiC, SiOCN, or SiBCN. In some embodimentsof the invention, the spacers 208 include silicon nitride. The spacers208 can be formed to a thickness of about 5 to 40 nm, although otherthicknesses are within the contemplated scope of the invention.

In some embodiments of the invention, source and drain regions 206 canbe epitaxially grown on exposed surfaces of the fins 104. In someembodiments of the invention, the source and drain regions 206 areformed to a thickness of about 4 nm to about 20 nm, for example 10 nm,although other thicknesses are within the contemplated scope of theinvention.

The source and drain regions 206 can be epitaxially grown using, forexample, vapor-phase epitaxy (VPE), molecular beam epitaxy (MBE),liquid-phase epitaxy (LPE), or other suitable processes. The source anddrain regions 206 can be semiconductor materials epitaxially grown fromgaseous or liquid precursors.

In some embodiments of the invention, the gas source for the epitaxialdeposition of semiconductor material includes a silicon containing gassource, a germanium containing gas source, or a combination thereof. Forexample, a Si layer can be epitaxially deposited (or grown) from asilicon gas source that is selected from the group consisting of silane,disilane, trisilane, tetrasilane, hexachlorodisilane, tetrachlorosilane,dichlorosilane, trichlorosilane, methylsilane, dimethylsilane,ethylsilane, methyldisilane, dimethyldisilane, hexamethyldisilane andcombinations thereof. A germanium layer can be epitaxially depositedfrom a germanium gas source that is selected from the group consistingof germane, digermane, halogermane, dichlorogermane, trichlorogermane,tetrachlorogermane and combinations thereof. A silicon germanium alloylayer can be epitaxially formed utilizing a combination of such gassources. Carrier gases like hydrogen, nitrogen, helium and argon can beused. In some embodiments of the invention, the epitaxial semiconductormaterials include carbon doped silicon (Si:C). This Si:C layer can begrown in the same chamber used for other epitaxy steps or in a dedicatedSi:C epitaxy chamber. The Si:C can include carbon in the range of about0.2 percent to about 3.0 percent.

Epitaxially grown silicon and silicon germanium can be doped by addingn-type dopants (e.g., phosphorus or arsenic) or p-type dopants (e.g.,Ga, B, BF2, or Al). In some embodiments of the invention, the source anddrain regions 206 can be epitaxially formed and doped by a variety ofmethods, such as, for example, in-situ doped epitaxy (doped duringdeposition), doped following the epitaxy, or by implantation and plasmadoping. The dopant concentration in the doped regions can range from1×10¹⁹ cm⁻³ to 2×10²¹ cm⁻³, or between 1×10²⁰ cm⁻³ and 1×10²¹ cm⁻³.

In some embodiments of the invention, the source and drain regions 206are made of silicon germanium. In some embodiments of the invention, thesource and drain regions 206 are made of silicon germanium having agermanium concentration of about 10 to about 65 percent, for example, 50percent, although other germanium concentrations are within thecontemplated scope of the invention. In some embodiments of theinvention of the invention, the source and drain regions 206 can extendabove a topmost surface of the fins 104.

As further depicted in FIG. 2A, the semiconductor structure 100 can alsoinclude one or more gate hard masks 210 (also referred to asself-aligned contact caps, or SAC caps) formed on each of the gates 102.The gate hard masks 210 can be made of any suitable material, such as,for example, silicon nitride.

As depicted in FIG. 2B, an interlayer dielectric 212 can be formed overthe semiconductor structure 100. The interlayer dielectric 212 can bemade of any suitable dielectric material, such as, for example, poroussilicates, carbon doped oxides, silicon dioxides, silicon nitrides,silicon oxynitrides, or other dielectric materials. Any known manner offorming the interlayer dielectric 212 can be utilized, such as, forexample, CVD, PECVD, ALD, flowable CVD, spin-on dielectrics, or PVD. Insome embodiments of the invention, the interlayer dielectric 212 and theSTI region 204 are made of the same dielectric material, and togetherdefine a single continuous dielectric region. In some embodiments of theinvention, the interlayer dielectric 212 is formed prior to a dummy gatepull and the formation of the gates 102.

In some embodiments of the invention, a hard mask 218 (sometimesreferred to as an oxide hard mask) can be formed over a surface of theinterlayer dielectric 212, a surface of the spacers 208, and/or asurface of the gate hard masks 210. The hard mask 218 can be made of anysuitable dielectric material, such as, for example, an oxide. Any knownmanner of forming the hard mask 218 can be utilized, such as, forexample, CVD, PECVD, ALD, flowable CVD, spin-on dielectrics, or PVD.

In some embodiments of the invention, an organic planarization layer(OPL) 214 can be formed over the hard mask 218. The OPL 214 can bepatterned to expose a surface of the gate hard masks 210 and a surfaceof the interlayer dielectric 212. The OPL 214 can be formed by a varietyof methods, such as, for example, CVD, PECVD, UHVCVD, RTCVD, MOCVD,LRPCVD, ALD, PVD, chemical solution deposition, MBE, or other likeprocess. In some embodiments of the invention, the OPL 214 can beapplied using, for example, spin coating technology.

The OPL 214 can be made from any suitable OPL material. In someembodiments of the invention, the OPL 214 can include a photo-sensitiveorganic polymer having a light-sensitive material that, when exposed toelectromagnetic (EM) radiation, is chemically altered. In other words,the OPL 214 can be configured to be removed using a developing solvent.For example, the photo-sensitive organic polymer can be polyacrylateresin, epoxy resin, phenol resin, polyamide resin, polyimide resin,unsaturated polyester resin, polyphenylenether resin,polyphenylenesulfide resin, or benzocyclobutene (BCB). In someembodiments of the invention, the OPL 214 can include any organicpolymer and/or a photo-active compound having a molecular structure thatcan attach to the molecular structure of the organic polymer. In someembodiments of the invention, the OPL 214 is planarized, using, forexample, a chemical-mechanical planarization (CMP) process. In someembodiments of the invention, the OPL 214 is a bottommost layer of apatterning stack (e.g., a tri-layer ARC stack having a photoresist andantireflective coating on the OPL 214).

As further depicted in FIG. 2A, exposed portions of the interlayerdielectric 212 can be removed to expose a surface of the source anddrain regions 206. Portions of the interlayer dielectric 212 can beremoved using any suitable method, such as a wet etch, a dry etch, or acombination of sequential wet and/or dry etches. In some embodiments ofthe invention, the interlayer dielectric 212 can be etched selective tothe spacers 208, and/or the gate hard masks 210. For example, dielectricmaterial (e.g., an oxide) can be etched using a directional RIEselective to SiN.

FIGS. 3A, 3B, and 3C depict cross-sectional views of the semiconductorstructure 100 taken along the lines X, X′, and Y of FIG. 1 after aprocessing operation according to one or more embodiments of theinvention. As illustrated in FIG. 3A, source/drain contacts 302(sometimes referred to as source/drain contact metals) can be formedover the source and drain regions 206.

The source/drain contacts 302 can be formed or deposited using knownmetallization techniques. In some embodiments of the invention, thesource/drain contacts 302 is overfilled above a surface of the gate hardmasks 210. The source/drain contacts 302 can be made of any suitableconducting material, such as, for example, metal (e.g., tungsten,titanium, tantalum, ruthenium, zirconium, cobalt, copper, aluminum,platinum), conducting metallic compound material (e.g., tantalumnitride, titanium nitride, tantalum carbide, titanium carbide, titaniumaluminum carbide, tungsten silicide, tungsten nitride, cobalt silicide,nickel silicide), conductive carbon, or any suitable combination ofthese materials. In some embodiments of the invention, the source/draincontacts 302 are cobalt or tungsten contacts. The conductive materialcan further include dopants that are incorporated during or afterdeposition. In some embodiments of the invention, the source/draincontacts 302 can include a barrier metal liner (not depicted). Materialexamples include tantalum nitride and tantalum (TaN/Ta), titanium,titanium nitride, cobalt, ruthenium, and manganese.

In some embodiments of the invention, the source/drain contacts 302 areplanarized after the deposition process, using for example, achemical-mechanical planarization. In some embodiments of the invention,the planarization process is configured to stop on the hard mask 218. Inother words, the source/drain contacts 302 can be planarized to asurface of the hard mask 218. In some embodiments of the invention, thisplanarization process can result in a recessing (thinning) of the hardmask 218. Stopping the planarization on the hard mask 218 leaves anoverburden of the source/drain contacts 302 above a surface of the gatehard masks 210. Advantageously, this overburden protects the activegates and the SAC cap (i.e., the gate hard masks 210) during thesubsequent interlayer dielectric etch (depicted in FIG. 4A).

FIGS. 4A, 4B, and 4C depict cross-sectional views of the semiconductorstructure 100 taken along the lines X, X′, and Y of FIG. 1 after aprocessing operation according to one or more embodiments of theinvention. As illustrated in FIG. 4B, the interlayer dielectric 212 canbe etched back (or recessed) to expose a surface of the gate hard masks210, sidewalls of the spacers 208, and/or sidewalls of the source/draincontacts 302.

The interlayer dielectric 212 can be recessed using any suitable method,such as a wet etch, a dry etch, or a combination of sequential wetand/or dry etches. In some embodiments of the invention, the interlayerdielectric 212 can be recessed selective to the source/drain contacts302, the spacers 208, and/or the gate hard masks 210. For example,dielectric material (e.g., an oxide) can be etched using a directionalRIE (or anisotropic etch) selective to Co, W, and/or SiN. In someembodiments of the invention, the dielectric etch back can result indamage to a top portion of the source/drain contacts 302, the spacers208, and/or the gate hard masks 210 not covered by the source/draincontacts 302 (the potentially damaged top portion is depicted above thedotted line in FIGS. 4A, 4B, and 4C). Advantageously, the active gates(i.e., the center gate depicted in FIG. 4A) are completely covered bythe source/drain contacts 302, and are consequently not exposed duringthe etch of the interlayer dielectric 212. As a result, the active gatesare not eroded during this process.

FIGS. 5A, 5B, and 5C depict cross-sectional views of the semiconductorstructure 100 taken along the lines X, X′, and Y of FIG. 1 after aprocessing operation according to one or more embodiments of theinvention. As illustrated in FIG. 5B, a dielectric layer 502 can beformed over the semiconductor structure 100. As discussed previouslyherein, the dielectric layer 502 can be made of an ultra low-kdielectric material (e.g., the dielectric layer 502 can be made of amaterial having a dielectric constant less than 3.0).

The dielectric layer 502 can be formed or deposited using knownprocesses, such as flowable dielectric deposition processes, spin-oncoatings, or other known processes. Example ultra low-k dielectricmaterials can include, for example, porous organosilicate glass (OSG),carbon-doped oxide (CDO), porous silicon dioxide, spin-on organicpolymeric dielectrics (e.g., polyimide, polynorbornenes,benzocyclobutene, and polytetrafluoroethylene (PTFE)), hydrogensilsesquioxane (HSQ), and methylsilsesquioxane (MSQ).

FIGS. 6A, 6B, and 6C depict cross-sectional views of the semiconductorstructure 100 taken along the lines X, X′, and Y of FIG. 1 after aprocessing operation according to one or more embodiments of theinvention. As illustrated in FIG. 6B, the semiconductor structure 100can be planarized below the potentially damaged surfaces of thesource/drain contacts 302, the spacers 208, and/or the gate hard masks210 (as depicted in FIGS. 4A, 4B, and 4C). The semiconductor structure100 can be planarized, using, for example, a chemical-mechanicalplanarization (CMP) process. As depicted in FIG. 6A, the source/draincontacts 302 can be recessed during this planarization process to alevel sufficient to define separate source/drain contacts 302 (i.e., twocontacts separated by a gate of the gates 102). In other words, thesemiconductor structure 100 can be planarized below a surface of theconnected overburden of the source/drain contacts 302.

FIGS. 7A, 7B, and 7C depict cross-sectional views of a semiconductorstructure 700 taken along the lines X, X′, and Y of FIG. 1 after aprocessing operation according to one or more embodiments of theinvention. FIGS. 7A, 7B, and 7C illustrate an alternative embodimentwhereby a selective cap 702 is formed over the source/drain contacts 302after the process steps depicted in FIGS. 3A, 3B, and 3C. In otherwords, the process depicted in FIGS. 7A, 7B, and 7C can proceed afterforming the source/drain contacts 302 over the source and drain regions206 as depicted in FIGS. 3A, 3B, and 3C.

As discussed previously herein, the selective cap 702 can provideadditional protection to the exposed surface of the source/draincontacts 302. As a result, the source/drain contacts 302 can betterprotect the covered gate hard masks 210 (i.e., the active gates). Theselective cap 702 can be deposited using, for example, a selectivedeposition process. For example, tungsten, ruthenium, and/or cobaltsilicide can be selectively deposited over the metal surface of thesource/drain contacts 302 (“selectively deposited” means that metalmaterials will only form on exposed metal surfaces, and will not formover dielectrics, such as the interlayer dielectric 212). The selectivecap 702 can be formed to a thickness of 5 to 50 nm, although otherthicknesses are within the contemplated scope of the invention.

FIGS. 8A, 8B, and 8C depict cross-sectional views of the semiconductorstructure 700 taken along the lines X, X′, and Y of FIG. 1 after aprocessing operation according to one or more embodiments of theinvention. As illustrated in FIG. 8B, the hard mask 218 can be removedand the interlayer dielectric 212 can be etched back (or recessed) toexpose a surface of the gate hard masks 210, sidewalls of the spacers208, and/or sidewalls of the source/drain contacts 302.

The interlayer dielectric 212 can be recessed using any suitable method,such as a wet etch, a dry etch, or a combination of sequential wetand/or dry etches. In some embodiments of the invention, the interlayerdielectric 212 can be recessed selective to the source/drain contacts302, the spacers 208, and/or the gate hard masks 210. For example,dielectric material (e.g., an oxide) can be etched using a directionalRIE selective to Co, W, and/or SiN. In some embodiments of theinvention, the selective cap 702 mitigates any damage to a top portionof the source/drain contacts 302, the spacers 208, and/or the gate hardmasks 210 caused by the etch back.

FIGS. 9A, 9B, and 9C depict cross-sectional views of the semiconductorstructure 700 taken along the lines X, X′, and Y of FIG. 1 after aprocessing operation according to one or more embodiments of theinvention. As illustrated in FIG. 9B, a dielectric layer 502 can beformed over the semiconductor structure 100. As discussed previouslyherein, the dielectric layer 502 can be made of an ultra low-kdielectric material (e.g., the dielectric layer 502 can be made of amaterial having a dielectric constant less than 3.0).

The dielectric layer 502 can be formed or deposited using knownprocesses, such as flowable dielectric deposition processes, spin-oncoatings, or other known processes. Example ultra low-k dielectricmaterials can include, for example, porous OSG, CDO, porous silicondioxide, spin-on organic polymeric dielectrics (e.g., polyimide,polynorbornenes, benzocyclobutene, and PTFE), HSQ, and MSQ

FIGS. 10A, 10B, and 10C depict cross-sectional views of thesemiconductor structure 700 taken along the lines X, X′, and Y of FIG. 1after a processing operation according to one or more embodiments of theinvention. As illustrated in FIG. 10B, the semiconductor structure 100can be planarized below the potentially damaged surfaces of thesource/drain contacts 302, the spacers 208, and/or the gate hard masks210 (as depicted in FIGS. 4A, 4B, and 4C). The semiconductor structure100 can be planarized, using, for example, a chemical-mechanicalplanarization (CMP) process. As depicted in FIG. 10A, the source/draincontacts 302 can be recessed during this planarization process to alevel sufficient to define separate source/drain contacts 302 (i.e., twocontacts separated by a gate of the gates 102). In other words, thesemiconductor structure 100 can be planarized below the selective cap702 and below a surface of the connected overburden of the source/draincontacts 302.

FIGS. 11A, 11B, and 11C depict cross-sectional views of a semiconductorstructure 1100 taken along the lines X, X′, and Y of FIG. 1 after aprocessing operation according to one or more embodiments of theinvention. FIGS. 11A, 11B, and 11C illustrate an alternative embodimentwhereby a liner 1102 is formed over the semiconductor structure 1100after the process steps depicted in FIGS. 4A, 4B, and 4C. In otherwords, the process depicted in FIGS. 11A, 11B, and 11C can proceed afterthe interlayer dielectric 212 etch back (or recess) exposes a surface ofthe gate hard masks 210, sidewalls of the spacers 208, and/or sidewallsof the source/drain contacts 302 as depicted in FIGS. 4A, 4B, and 4C.

As discussed previously herein, the liner 1102 can mitigate damage tothe gate hard masks 210, the spacers 208, and/or the source/draincontacts 302 caused by the interlayer dielectric etch back. The liner1102 can also serve as a diffusion barrier, protecting the source/draincontacts 302 from dielectric diffusion (i.e., the formation ofmetal-oxides) from the dielectric layer 502 (depicted in FIG. 12B). Insome embodiments of the invention, the liner 1102 is conformallydeposited over a surface of the source/drain contacts 302, a surface ofthe gate hard masks 210, a surface of the spacers 208, a surface of theSTI region 204, and a surface of the interlayer dielectric 212. In someembodiments of the invention, the liner 1102 is formed using a CVD,PECVD, UHVCVD, RTCVD, MOCVD, LPCVD, LRPCVD, ALD, PVD, chemical solutiondeposition, MBE, or other like process. The liner 1102 can be made ofany suitable material, such as, for example, a low-k dielectric, anitride, silicon nitride, SiON, SiC, SiOCN, or SiBCN. In someembodiments of the invention, the liner 1102 includes silicon nitride.The liner 1102 can be formed to a thickness of about 5 nm or less, or 3nm or less, although other thicknesses are within the contemplated scopeof the invention.

FIGS. 12A, 12B, and 12C depict cross-sectional views of thesemiconductor structure 1100 taken along the lines X, X′, and Y of FIG.1 after a processing operation according to one or more embodiments ofthe invention. As illustrated in FIG. 12B, a dielectric layer 502 can beformed over the semiconductor structure 100. As discussed previouslyherein, the dielectric layer 502 can be made of an ultra low-kdielectric material (e.g., the dielectric layer 502 can be made of amaterial having a dielectric constant less than 3.0).

The dielectric layer 502 can be formed or deposited using knownprocesses, such as flowable dielectric deposition processes, spin-oncoatings, or other known processes. Example ultra low-k dielectricmaterials can include, for example, porous OSG, CDO, porous silicondioxide, spin-on organic polymeric dielectrics (e.g., polyimide,polynorbornenes, benzocyclobutene, and PTFE), HSQ, and MSQ.

FIGS. 13A, 13B, and 13C depict cross-sectional views of thesemiconductor structure 1100 taken along the lines X, X′, and Y of FIG.1 after a processing operation according to one or more embodiments ofthe invention. As illustrated in FIG. 13B, the semiconductor structure100 can be planarized below the potentially damaged surfaces of thesource/drain contacts 302, the spacers 208, and/or the gate hard masks210 (as depicted in FIGS. 4A, 4B, and 4C). The semiconductor structure100 can be planarized, using, for example, a chemical-mechanicalplanarization (CMP) process. As depicted in FIG. 13A, the source/draincontacts 302 can be recessed during this planarization process to alevel sufficient to define separate source/drain contacts 302 (i.e., twocontacts separated by a gate of the gates 102). In other words, thesemiconductor structure 100 can be planarized below a surface of theconnected overburden of the source/drain contacts 302.

FIG. 14 depicts a flow diagram 1400 illustrating a method for forming asemiconductor device according to one or more embodiments of theinvention. As shown at block 1402, a gate is formed over a channelregion of a fin. The gate can include a gate hard mask and a gatespacer. In some embodiments of the invention, the gate hard maskincludes silicon nitride.

At block 1404, a source is formed adjacent to a first end of the channelregion and a drain is formed adjacent to a second end of the channelregion. In some embodiments of the invention (e.g., an RMG process), thesource and drain can be formed before metal gate formation (i.e., whilethe dummy gate is in place).

At block 1406, a contact is formed on the gate hard mask. The contactcan include a first portion on a surface of the source and a secondportion on a surface of the drain. In some embodiments of the invention,the contact includes cobalt or tungsten. In some embodiments of theinvention, the contact includes an overburden that covers a gate hardmask. As discussed previously herein, the contact can prevent erosion ofthe gate hard mask when recessing the first dielectric layer at block1410.

At block 1408, a first dielectric layer is formed on a sidewall of thegate spacer. The first dielectric layer can include a first dielectricmaterial having a first dielectric constant. In some embodiments of theinvention, the first dielectric material includes silicon oxide and thefirst dielectric constant is about 3. In some embodiments of theinvention, the first dielectric layer is formed on sidewalls of a dummygate that is subsequently replaced by the gate (e.g., a metal gate)during an RMG module.

At block 1410, the first dielectric layer is recessed to expose asidewall of the contact and a sidewall of the gate spacer. In someembodiments of the invention, recessing the first dielectric layerincludes an etch back, such as previously described with respect to FIG.4B. In some embodiments of the invention, the etch back is selective toa material of the SAC cap and/or a material of the gate hard mask. Insome embodiments of the invention, the etch back damages a top portionof the SAC cap, but does not damage the covered active gates, asdiscussed previously herein.

At block 1412, a second dielectric layer is formed on a recessed surfaceof the first dielectric layer. The second dielectric layer can include asecond dielectric material having a second dielectric constant less thanthe first dielectric constant. In some embodiments of the invention, thesecond dielectric material includes a low-k dielectric material and thesecond dielectric constant is less than 3.

The method can further include forming an oxide hard mask on a surfaceof the gate hard mask and planarizing the contact to a surface of theoxide hard mask such that an overburden remains over the gate hard mask.In this manner, a contact overburden protects the gate hard mask fromerosion.

In some embodiments of the invention, the method includes selectivelydepositing a selective cap on a surface of the contact. The selectivecap can be formed in a similar manner as described previously hereinwith respect to FIGS. 7A, 7B, and 7C.

In some embodiments of the invention, the method includes depositing aliner over a surface of the contact, a surface of the gate hard mask,and on the recessed surface of the first dielectric layer. The liner canbe formed in a similar manner as described previously herein withrespect to FIGS. 11A, 11B, and 11C.

FIG. 15 depicts a flow diagram 1500 illustrating a method for forming asemiconductor device according to one or more embodiments of theinvention. As shown at block 1502, a gate is formed over a channelregion of a fin. The gate can include a gate hard mask and a gatespacer. In some embodiments of the invention, the gate hard maskincludes silicon nitride.

At block 1504, a SAC cap is formed over the gate. In some embodiments ofthe invention, the SAC cap includes silicon nitride. At block 1506, acontact is formed on the SAC cap. The contact can include, for example,tungsten or cobalt. In some embodiments of the invention, the contactincludes an overburden that covers the SAC cap. As discussed previouslyherein, the contact can prevent erosion of the SAC cap when recessingthe first dielectric layer at block 1510.

At block 1508, a first dielectric layer is formed on a sidewall of thegate. The first dielectric layer can include a first dielectric materialhaving a first dielectric constant. In some embodiments of theinvention, the first dielectric material includes silicon oxide and thefirst dielectric constant is about 3. In some embodiments of theinvention, the first dielectric layer is formed on sidewalls of a dummygate that is subsequently replaced by the gate (e.g., a metal gate)during an RMG module.

At block 1510, the first dielectric layer is recessed to expose asidewall of the contact. In some embodiments of the invention, recessingthe first dielectric layer includes an etch back, such as previouslydescribed with respect to FIG. 4B. In some embodiments of the invention,the etch back is selective to a material of the SAC cap and/or amaterial of the gate hard mask. In some embodiments of the invention,the etch back damages a top portion of the SAC cap, but does not damagethe covered active gates, as discussed previously herein.

At block 1512, a second dielectric layer is formed on a recessed surfaceof the first dielectric layer. The second dielectric layer can include asecond dielectric material having a second dielectric constant less thanthe first dielectric constant. In some embodiments of the invention, thesecond dielectric material includes a low-k dielectric material and thesecond dielectric constant is less than 3.

The methods and resulting structures described herein can be used in thefabrication of IC chips. The resulting IC chips can be distributed bythe fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includes ICchips, ranging from toys and other low-end applications to advancedcomputer products having a display, a keyboard or other input device,and a central processor.

Various embodiments of the present invention are described herein withreference to the related drawings. Alternative embodiments can bedevised without departing from the scope of this invention. Althoughvarious connections and positional relationships (e.g., over, below,adjacent, etc.) are set forth between elements in the followingdescription and in the drawings, persons skilled in the art willrecognize that many of the positional relationships described herein areorientation-independent when the described functionality is maintainedeven though the orientation is changed. These connections and/orpositional relationships, unless specified otherwise, can be direct orindirect, and the present invention is not intended to be limiting inthis respect. Similarly, the term “coupled” and variations thereofdescribes having a communications path between two elements and does notimply a direct connection between the elements with no interveningelements/connections between them. All of these variations areconsidered a part of the specification. Accordingly, a coupling ofentities can refer to either a direct or an indirect coupling, and apositional relationship between entities can be a direct or indirectpositional relationship. As an example of an indirect positionalrelationship, references in the present description to forming layer “A”over layer “B” include situations in which one or more intermediatelayers (e.g., layer “C”) is between layer “A” and layer “B” as long asthe relevant characteristics and functionalities of layer “A” and layer“B” are not substantially changed by the intermediate layer(s).

The following definitions and abbreviations are to be used for theinterpretation of the claims and the specification. As used herein, theterms “comprises,” “comprising,” “includes,” “including,” “has,”“having,” “contains” or “containing,” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, acomposition, a mixture, process, method, article, or apparatus thatcomprises a list of elements is not necessarily limited to only thoseelements but can include other elements not expressly listed or inherentto such composition, mixture, process, method, article, or apparatus.

Additionally, the term “exemplary” is used herein to mean “serving as anexample, instance or illustration.” Any embodiment or design describedherein as “exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or designs. The terms “at least one”and “one or more” are understood to include any integer number greaterthan or equal to one, i.e. one, two, three, four, etc. The terms “aplurality” are understood to include any integer number greater than orequal to two, i.e. two, three, four, five, etc. The term “connection”can include an indirect “connection” and a direct “connection.”

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedcan include a particular feature, structure, or characteristic, butevery embodiment may or may not include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

For purposes of the description hereinafter, the terms “upper,” “lower,”“right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” andderivatives thereof shall relate to the described structures andmethods, as oriented in the drawing figures. The terms “overlying,”“atop,” “on top,” “positioned on” or “positioned atop” mean that a firstelement, such as a first structure, is present on a second element, suchas a second structure, wherein intervening elements such as an interfacestructure can be present between the first element and the secondelement. The term “direct contact” means that a first element, such as afirst structure, and a second element, such as a second structure, areconnected without any intermediary conducting, insulating orsemiconductor layers at the interface of the two elements.

Spatially relative terms, e.g., “beneath,” “below,” “lower,” “above,”“upper,” and the like, are used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device can be otherwise oriented (e.g., rotated 90degrees or at other orientations), and the spatially relativedescriptors used herein should be interpreted accordingly.

The terms “about,” “substantially,” “approximately,” and variationsthereof, are intended to include the degree of error associated withmeasurement of the particular quantity based upon the equipmentavailable at the time of filing the application. For example, “about”can include a range of ±8% or 5%, or 2% of a given value.

The phrase “selective to,” such as, for example, “a first elementselective to a second element,” means that the first element can beetched and the second element can act as an etch stop.

The term “conformal” (e.g., a conformal layer or a conformal deposition)means that the thickness of the layer is substantially the same on allsurfaces, or that the thickness variation is less than 15% of thenominal thickness of the layer.

The terms “epitaxial growth and/or deposition” and “epitaxially formedand/or grown” mean the growth of a semiconductor material (crystallinematerial) on a deposition surface of another semiconductor material(crystalline material), in which the semiconductor material being grown(crystalline overlayer) has substantially the same crystallinecharacteristics as the semiconductor material of the deposition surface(seed material). In an epitaxial deposition process, the chemicalreactants provided by the source gases can be controlled and the systemparameters can be set so that the depositing atoms arrive at thedeposition surface of the semiconductor substrate with sufficient energyto move about on the surface such that the depositing atoms orientthemselves to the crystal arrangement of the atoms of the depositionsurface. An epitaxially grown semiconductor material can havesubstantially the same crystalline characteristics as the depositionsurface on which the epitaxially grown material is formed. For example,an epitaxially grown semiconductor material deposited on a {100}orientated crystalline surface can take on a {100} orientation. In someembodiments of the invention of the invention, epitaxial growth and/ordeposition processes can be selective to forming on semiconductorsurface, and may or may not deposit material on exposed surfaces, suchas silicon dioxide or silicon nitride surfaces.

As previously noted herein, for the sake of brevity, conventionaltechniques related to semiconductor device and integrated circuit (IC)fabrication may or may not be described in detail herein. By way ofbackground, however, a more general description of the semiconductordevice fabrication processes that can be utilized in implementing one ormore embodiments of the present invention will now be provided. Althoughspecific fabrication operations used in implementing one or moreembodiments of the present invention can be individually known, thedescribed combination of operations and/or resulting structures of thepresent invention are unique. Thus, the unique combination of theoperations described in connection with the fabrication of asemiconductor device according to the present invention utilize avariety of individually known physical and chemical processes performedon a semiconductor (e.g., silicon) substrate, some of which aredescribed in the immediately following paragraphs.

In general, the various processes used to form a micro-chip that will bepackaged into an IC fall into four general categories, namely, filmdeposition, removal/etching, semiconductor doping andpatterning/lithography. Deposition is any process that grows, coats, orotherwise transfers a material onto the wafer. Available technologiesinclude physical vapor deposition (PVD), chemical vapor deposition(CVD), electrochemical deposition (ECD), molecular beam epitaxy (MBE)and more recently, atomic layer deposition (ALD) among others.Removal/etching is any process that removes material from the wafer.Examples include etch processes (either wet or dry), chemical-mechanicalplanarization (CMP), and the like. Reactive ion etching (RIE), forexample, is a type of dry etching that uses chemically reactive plasmato remove a material, such as a masked pattern of semiconductormaterial, by exposing the material to a bombardment of ions thatdislodge portions of the material from the exposed surface. The plasmais typically generated under low pressure (vacuum) by an electromagneticfield. Semiconductor doping is the modification of electrical propertiesby doping, for example, transistor sources and drains, generally bydiffusion and/or by ion implantation. These doping processes arefollowed by furnace annealing or by rapid thermal annealing (RTA).Annealing serves to activate the implanted dopants. Films of bothconductors (e.g., poly-silicon, aluminum, copper, etc.) and insulators(e.g., various forms of silicon dioxide, silicon nitride, etc.) are usedto connect and isolate transistors and their components. Selectivedoping of various regions of the semiconductor substrate allows theconductivity of the substrate to be changed with the application ofvoltage. By creating structures of these various components, millions oftransistors can be built and wired together to form the complexcircuitry of a modern microelectronic device. Semiconductor lithographyis the formation of three-dimensional relief images or patterns on thesemiconductor substrate for subsequent transfer of the pattern to thesubstrate. In semiconductor lithography, the patterns are formed by alight sensitive polymer called a photo-resist. To build the complexstructures that make up a transistor and the many wires that connect themillions of transistors of a circuit, lithography and etch patterntransfer steps are repeated multiple times. Each pattern being printedon the wafer is aligned to the previously formed patterns and slowly theconductors, insulators and selectively doped regions are built up toform the final device.

The flowchart and block diagrams in the Figures illustrate possibleimplementations of fabrication and/or operation methods according tovarious embodiments of the present invention. Variousfunctions/operations of the method are represented in the flow diagramby blocks. In some alternative implementations, the functions noted inthe blocks can occur out of the order noted in the Figures. For example,two blocks shown in succession can, in fact, be executed substantiallyconcurrently, or the blocks can sometimes be executed in the reverseorder, depending upon the functionality involved.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments described. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdescribed herein.

What is claimed is:
 1. A method for forming a semiconductor device, themethod comprising: forming a gate over a channel region of a fin, thegate comprising a gate spacer and a gate hard mask; forming a sourceadjacent to a first end of the channel region and a drain adjacent to asecond end of the channel region; forming a contact on the gate hardmask, the contact comprising a first portion on a surface of the sourceand a second portion on a surface of the drain; forming a firstdielectric layer on a sidewall of the gate spacer, the first dielectriclayer comprising a first dielectric material having a first dielectricconstant; recessing the first dielectric layer to expose a sidewall ofthe contact and a sidewall of the gate spacer; and forming a seconddielectric layer on a recessed surface of the first dielectric layer,the second dielectric layer comprising a second dielectric materialhaving a second dielectric constant less than the first dielectricconstant.
 2. The method of claim 1, wherein the contact prevents erosionof the gate hard mask when recessing the first dielectric layer.
 3. Themethod of claim 1 further comprising forming an oxide hard mask on asurface of the gate hard mask.
 4. The method of claim 3 furthercomprising planarizing the contact to a surface of the oxide hard masksuch that an overburden remains over the gate hard mask.
 5. The methodof claim 1, wherein the contact comprises cobalt or tungsten and thegate hard mask comprises silicon nitride.
 6. The method of claim 1,wherein the first dielectric material comprises silicon oxide and thefirst dielectric constant is about
 3. 7. The method of claim 6, whereinthe second dielectric material comprises a low-k dielectric material andthe second dielectric constant is less than
 3. 8. The method of claim 2,wherein recessing the first dielectric layer damages a top portion ofthe contact.
 9. The method of claim 1 further comprising selectivelydepositing a selective cap on a surface of the contact.
 10. The methodof claim 1 further comprising depositing a liner over a surface of thecontact and on the recessed surface of the first dielectric layer.
 11. Amethod for forming a semiconductor device, the method comprising:forming a gate over a channel region of a fin; forming a self-alignedcontact (SAC) cap over the gate; forming a contact on the SAC cap;forming a first dielectric layer on a sidewall of the gate, the firstdielectric layer comprising a first dielectric material having a firstdielectric constant; recessing the first dielectric layer to expose asidewall of the contact; and forming a second dielectric layer on arecessed surface of the first dielectric layer, the second dielectriclayer comprising a second dielectric material having a second dielectricconstant less than the first dielectric constant.
 12. The method ofclaim 11, wherein the first dielectric material comprises silicon oxideand the first dielectric constant is about
 3. 13. The method of claim12, wherein the second dielectric material comprises a low-k dielectricmaterial and the second dielectric constant is less than
 3. 14. Themethod of claim 11 further comprising planarizing the contact such thatan overburden remains over the SAC cap.
 15. The method of claim 11further comprising selectively depositing a selective cap on a surfaceof the contact.
 16. The method of claim 11 further comprising depositinga liner over a surface of the SAC cap, a surface of the contact, and onthe recessed surface of the first dielectric layer.
 17. A semiconductordevice comprising: a gate over a channel region of a fin, the gatecomprising a gate spacer and a gate hard mask; a source adjacent to afirst end of the channel region and a drain adjacent to a second end ofthe channel region; a first contact on a surface of the source and asecond contact on a surface of the drain; a first dielectric layer on asidewall of the first contact and on a sidewall of the second contact,the first dielectric layer comprising a first dielectric material havinga first dielectric constant; and a second dielectric layer on a surfaceof the first dielectric layer, the second dielectric layer comprising asecond dielectric material having a second dielectric constant less thanthe first dielectric constant; wherein a first portion of the seconddielectric layer is on a sidewall of the gate spacer and a secondportion of the second dielectric layer is on the sidewall of the firstcontact and on the sidewall of the second contact.
 18. The semiconductordevice of claim 17, wherein the first dielectric material comprisessilicon oxide and the first dielectric constant is about
 3. 19. Thesemiconductor device of claim 18, wherein the second dielectric materialcomprises a low-k dielectric material and the second dielectric constantis less than
 3. 20. The semiconductor device of claim 17 furthercomprising a liner between the second dielectric layer and the gatespacer.